BOLT-SOCKET HEAD 8T3957 - Caterpillar

Illustration 1 g03746847
Diesel Exhaust Fluid (DEF) dosing control cabinet componentsValves are shown in a static state (1) DEF line to injector at Clean Emissions Module (CEM) (2) Air line to injector at CEM (3) Compressed air source (customer supplied) (4) DEF source (customer supplied) (5) DEF pressure sensor (6) Air assist pressure sensor (7) Air pressure regulator (8) Air assist valve (9) DEF buffer tank return valve (10) DEF buffer tank fill valve (11) DEF pump (12) DEF level sensor (13) DEF buffer tankDEF Buffer Tank
The Diesel Exhaust Fluid (DEF) buffer tank is located within the dosing cabinet. DEF is supplied to the DEF buffer tank from the remote DEF tank that is supplied by the customer.The DEF buffer tank contains a DEF level sensor and temperature sensor. This sensor sits in the DEF buffer tank and reads the level of the DEF within the buffer tank and the DEF temperature.When the DEF tank level sensor reads below a certain threshold, the DEF tank refill valve will open and allow the DEF buffer tank to refill. Once the level passes above a threshold, the DEF tank refill valve will close.DEF Pump
The DEF pump is located in the dosing cabinet. The DEF pump is powered by a 120 VAC power source.The Electronic Control Module (ECM) controls the DEF pump by sending a Pulse Width Modulated (PWM) signal to the pump.The DEF pump is a fixed displacement pump. The higher the duty cycle of the PWM signal, the more DEF is dosed into the exhaust stream.Air Manifold
The air manifold is where all of the air connections to the dosing cabinet are made.The air manifold contains internal passages for the air and contains the air assist valve and the air pressure regulator.DEF Manifold
The DEF manifold is where all of the DEF connections to the dosing cabinet are made.The DEF manifold contains internal passages for the DEF and contains the solenoids required for operation of the DEF manifold portion of the dosing system.DEF Lines
The DEF lines are connected to the dosing cabinet.The DEF supply line is routed from the remote customer tank to the DEF inlet on the dosing cabinet.The DEF injector supply line is routed from the outlet of the dosing cabinet to the DEF injector on the Clean Emissions Module (CEM).Both of these lines are supplied by the customer.Preparing Dosing Readiness
The Selective Catalyst Reduction (SCR) dosing system checks the operation of the air assist valve, DEF control valves, and DEF dosing pump.The system will annunciate a fault code for any unexpected voltage, current, or pressure values.The system will continue to cycle the valves until all indications determine the system is ready to dose DEF.Step 1 Preparing Dosing Readiness
The air assist valve is energized causing the valve to open. The resulting air pressure is measured at the DEF pressure sensor. The DEF buffer tank return valve is energized causing the DEF buffer tank return valve to close.This action is taken to check for the following conditions:
Blockage in the DEF lines
Stuck DEF buffer